1. Field of the Invention
The present invention generally relates to filter cartridges for water or beverages, such as those used in water, ice-water, soda pop machines, or other beverage dispensers. Specifically, the invention is a filter assembly, for cooperation with a filter head/manifold, that includes a filter cartridge substantially comprising recyclable components. More specifically, the invention relates to a filter assembly that allows all or substantially all of the surfaces that contact liquid to be periodically removed and recycled, thereby reducing the chance of contamination from long-term use of the surfaces. The filter cartridge is substantially non-pressure bearing, except for the neck of the filter cartridge that extends to form a liquid seal with the head/manifold or optionally except for the cap of the filter cartridge including the neck. A pressure vessel substantially surrounds the filter cartridge for holding and supporting the walls of the filter cartridge under liquid pressure, but the pressure vessel does not necessarily liquid-seal to the filter cartridge or the filter head/manifold.
2. Related Art
Many filter systems for water or other liquid filtration comprise a filter that cooperates with a “filter head,” which term herein includes a fluid manifold, valve head, or other connection device that directs fluid to and from the filter. The filter typically seals to an internal surface of the filter head so that the liquid entering the filter head flows into the filter, through the filter, then out of the filter to an outlet port in the filter head. In the United States and Canada, water filters are typically required to contain and withstand pressures of about 500 psi without rupturing. In the United States, water systems typically operate in the range of 40-125 psi, and NSF (National Sanitation Foundation) approval ratings typically require a water filter to withstand 4 times the claimed maximum operating pressure, or typically 500 psi. In Canada, safety factors require that water filters withstand about 508 psi for one minute. In Europe, some safety preferences dictate a burst pressure of no less than 475 psi.
In one general type of filter system, a disposable pressure vessel connects directly to a filter head. In such a system, when the filter media inside the pressure vessel is spent, the entire pressure vessel must be discarded, including the media contained therein. Disposable pressure vessels are not easily recyclable as there are no easy means to disassemble the pressure vessel. The disposable pressure vessel outer wall is entirely pressure-bearing, that is, it may safely withstand the liquid pressure of the particular system with a large safety margin. Therefore, disposable pressure vessels are more costly to replace because they use more plastic or more expensive materials such as aluminum. Use of disposable pressure vessels is, therefore, costly in terms of filter expense and environmental impact.
In alternative filter systems, a disposable filter cartridge may be supplied inside a pressure-bearing housing that connects to the filter head. In such a system, the pressure-bearing housing typically seals to the head using o-rings or other seals and surfaces that are contacted by the liquid being filtered. When the media of the filter cartridge is spent, the filter cartridge is typically discarded and replaced with another cartridge. The conventional filter cartridge has few recyclable components, and, the few recyclable components of the cartridge, such as granular carbon contained in the cartridge, are not removable or easily accessible to a person who might want to recycle. While the filter cartridge is removed and thrown away, the thick-walled pressure vessel is reused. During use, portions of the pressure vessel come in contact with the liquid being filtered, and, therefore, the pressure vessel may become contaminated with bacteria or other unhealthy substances. Because the pressure vessel is continually reused, the contaminated portions remain in use in the filter system and can further the contamination problem in the filter system and in the liquid flowing through it.
Therefore, there is a need for an improved filter cartridge, which is substantially recyclable and which, therefore, reduces the resource and environmental created by the filter cartridge. Also, there is a need for an economical and efficient filter cartridge that is designed so that every time the filter cartridge is removed for recycling, the surfaces with the highest chance of being contaminated are also replaced. The filter assembly of the present invention fulfills these needs.